The field of the invention is rotary position transducers such as incremental position encoders that monitor shaft rotation.
There are numerous applications where a knob or crank is manually turned to carry out a control function. In a numerically controlled machine tool, for example, a handwheel may be provided on the control panel to enable the operator to manually "jog" the cutting tool along one or more axes of motion. The amount of handwheel rotation is translated into a digital quantity which is employed to drive the appropriate servomechanism the desired distance.
In prior control systems incremental shaft encoders are employed to translate the handwheel position into a digital quantity suitable for driving the servomechanism. While such encoders work well, they are expensive, precision instruments. In addition, mechanical detent mechanisms must be attached to the shaft of such encoders to provide the user with the proper touch, or feel. Such mechanical mechanisms add further complexity and cost and reduce the overall reliability of the system.